Several reactions that participate in the conjugation of amines are under investigation. Although the reactions are different, each participates in the detoxication of the vast number of xenobiotics to which man is exposed. Methylation of amino groups is catalyzed by a group of amine N-methyltransferases. Two such enzymes have been prepared in a homogeneous state from rabbit liver and have allowed an analysis of the spectrum of substrates for which S-adenosyl-L-methionine serves as methyl donor. The two N-methyltransferases are proteins of approximately the same size (29,000 daltons) and similar isoelectric point but are separable from each other. They have an overlapping specificity for methyl group acceptors that includes most aromatic primary amines and secondary amines, as well as aliphatic compounds. These enzymes, originally designated as indolethylamine N-methyltransferases or arylamine N-methyltransferase, can now be said to be general amine N-methyltransferases of the broad specificity usually associated with the enzymes of detoxication. Sulfation of amino groups is catalyzed by enzymes being isolated from guinea pig liver for which phosphoadenosylphosphosulfate serves as the sulfuryl group donor. The investigation has uncovered a number of aryl as well as alkyl amines, including both primary and secondary amines, that act as acceptor.